WASHINGTON — John Kerry was the center of attention during his first Cabinet meeting as secretary of state. A White House photo shows him speaking, hands outstretched and eyes wide open as President Obama looked on.

Off in the corner, barely visible, was another man. His hand was over his mouth as he leaned back and listened. That man, overshadowed as ever, was Kerry’s younger brother, Cameron.

Throughout his life, Cam, as his friends call him, has been devoted to his older brother’s political career, helping him run his campaigns and advising on matters big and small.

During a fund-raiser in 2004, Kerry supporters printed up a giant banner emblazoned with, “Cameron Kerry for First Brother.”

Now, Cameron is briefly on closer-to-equal footing — and making history, even if for only a few weeks. As general counsel at the Department of Commerce, he recently became acting secretary of the department while waiting confirmation of a new nominee, marking the first time two brothers are serving at the same time in a presidential Cabinet.

“I have to say, two Kerrys are even better than one,” Vice President Joe Biden said in a statement to the Globe.

The history-making move is also proving that, well, having two Secretary Kerrys can get quite confusing.

In the Commerce Department, where officialdom prohibits first name usage, staffers have started referring to John Kerry as “the other Secretary Kerry.” When appointments are made at the White House Mess, they now have to specify which Secretary Kerry the reservation is for – and, when paying, Cameron Kerry has been tempted to simply say, “Just put it on his tab.”

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Senator John Kerry bounded over his brother, Cameron Kerry on the Esplanade in Boston in 2004. Throughout his life, Cameron has been dedicated to his brother’s politcal career.

‘Look, I am proud to be John’s brother. I don’t feel that fully defines me, and I’m confident enough in my own abilities.’

Last week, Cameron and John Kerry both signed off on a diplomatic cable to be sent to missions overseas that house employees of both the Commerce and State Departments. The cable said, in all caps, it was from “Secretary Kerry and Acting Secretary of Commerce Kerry.”

“Which is going to confuse the hell out of some people in missions abroad,” Cameron Kerry said.

But beyond marking a historical footnote, the dual appointments highlights the journey of two brothers, whose relationship has evolved from political debates around the family dining room table to, now, debates inside the West Wing of the White House.

The brothers are studies in both similarities and contrasts. Close your eyes, and you could mistake one for the other, with their similarly halting speech. But Cameron is like a less pronounced version of John. His face is not as angular, his curly hair is not as groomed.

John went to Yale, Cameron went to Harvard; John is Catholic, while Cameron converted to Judaism when he married his wife in 1983. Having spent formative years abroad while their father was a diplomat, the brothers have been known to speak in French when they didn’t want those around them to know what they were saying.

“I think everyone respects Cameron as a quiet, thoughtful person,” said Massachusetts Secretary of State William F. Galvin. “Not that John’s noisy but he’s certainly the more outgoing. Cameron’s more of a ponderer.”

The only time Cameron Kerry publicly weighed running for office was in 2006, when Galvin was considering running for governor and Kerry began laying the groundwork for a secretary of state campaign.

“When [Galvin] decided he was going to stay put, I felt like as the younger brother of a sitting senator, I couldn’t run against an incumbent,” Kerry said.

There have been siblings in powerful federal positions before, of course. President John F. Kennedy named his brother, Robert, to be attorney general. Secretary of State John Foster Dulles’s younger brother Allen ran the CIA in the 1950s — making them a more powerful brotherly duo than the Kerrys — but the CIA director was not a Cabinet position. The Kerrys are still a first for brothers leading Cabinet departments.

Cameron spent much of his career as a lawyer at Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, the high-powered Boston-based law firm. Then, in 2009, he was named as the Commerce Department’s general counsel, the agency’s third-ranking position.

His attendance at the Cabinet meeting in February came when he represented the agency at the meeting. On June 1, Cameron was named acting secretary, triggering a “Congratulations, Mr. Secretary” phone call from his brother.

But the position is likely to be shortlived. Obama’s nominee, Hyatt Hotel heiress Penny Pritzker, has so far had a smooth confirmation process and a vote by the full Senate could come soon.

As a result, Kerry is not getting too comfortable in his new office. The reception area outside of it still features a large photo of the previous acting secretary, Rebecca Blank. The inside is sparse, with only a few family photos around his desk (along with a large sword inscribed with his name, a gift from the Qatar attorney general that he has used to cut cakes).

Once a permanent commerce secretary is confirmed, Kerry plans to go back to being the agency’s general counsel.

The brothers’ respective offices are several blocks from each other, with the White House in the middle. Cameron said they keep in frequent touch; his brother texts him photos from around the globe, such as the one John sent him from the Brandenburg Gate.

“When we found ourselves in our first Cabinet meeting earlier this year, I was again reminded of how proud our parents would’ve been of all he’s achieved,” John Kerry said.

Obama made a “big deal” about the fact that the brothers were together, and after the Cabinet meeting ended, the brothers walked out of the West Wing, stopping to “take it all in,” said their long time friend, Alan Solomont, who talked later with Cameron about the Cabinet meeting.

Cameron, who at 62 is seven years younger than his brother, has been involved in his brother’s political career since its inception.

After John Kerry returned from his naval service in the Vietnam War, he famously testified against the conflict in a hearing of the Senate Foreign Relations Committee. In the back of the room sat 19-year-old Cameron. When John Kerry launched a congressional campaign shortly after, Cameron Kerry helped run it.

During that 1972 campaign, Cameron was arrested the night before the Democratic primary for breaking into the basement of the building that housed the headquarters of both Kerry and one of his primary rivals. After finding Cameron and another campaign worker near the building’s phone system, police arrested the pair on charges of breaking and entering.

Stripped across the front page of the Lowell Sun was a headline, “Kerry Brother Arrested in Lowell ‘Watergate.’ ” The Kerrys then and now have said that they were set up, with an anonymous call coming in minutes earlier threatening to cut the Kerry campaign’s phone lines the day before get-out-the vote efforts. Charges against Cameron Kerry were later dropped.

Cameron says he does not mind being overshadowed by his older brother.

“Look, I am proud to be John’s brother,” Cameron Kerry said. “I don’t feel that fully defines me, and I’m confident enough in my own abilities and relationships that I don’t feel that that’s anything to be ashamed of.”

Nonetheless, as Cameron Kerry wrote in an e-mail, “He’ll still be Secretary Kerry long after people stop calling me that.”